Combination down hole tool

ABSTRACT

A series of down hole tools are assembled from a common subassembly to which are added various specialty parts to make a flow back plug, a bridge plug or a plug with a disintegratable check valve. The subassembly may be used, as is, as a ball drop plug. The components may be added through either end of the subassembly without having to take the subassembly apart. The subassembly and specialty parts may be shipped to the customer so the end user may customize the subassembly to provide a plug operable to provide a variety of functions.

This application is based on U.S. Provisional Application 61/214,347filed Apr. 21, 2009priority of which is claimed.

This invention relates to a tool used in wells extending into the earthand, more particularly, to a series of down hole tools based on a commonsubassembly.

BACKGROUND OF THE INVENTION

This invention is a modification or improvement over the devices shownin U.S. patent application Ser. No. 12/317,497filed

December 23, 2008, the disclosure of which is incorporated herein byreference.

An important development in natural gas production in recent decades hasbeen the drilling of horizontal legs of hydrocarbon wells in combinationwith improvements in hydraulic fracturing techniques for stimulatingproduction from previously uneconomically tight formations. For someyears, the fastest growing segment of gas production has been fromshales or very silty zones that previously have not been consideredeconomic. The current areas of increasing activity include the BarnettShale, the Haynesville Shale, the Fayetteville Shale, the MarcellusShale and other shale or shaley formations.

There are a variety of down hole tools used in the completion and/orproduction of hydrocarbon wells such as bridge plugs, flow back plugs,ball drop plugs and the like. In the past, these have all been toolsspecially designed for a single purpose.

It is no exaggeration to say that the future of natural gas productionin the continental United States is from heretofore uneconomically tightgas bearing formations, many of which are shales or shaley silty zones.Accordingly, a development that allows effective frac jobs at overalllower costs is important.

SUMMARY OF THE INVENTION

As disclosed herein, there is provided a common subassembly that caneasily be assembled with specialty parts to provide a bridge plug, aball drop plug, or a plug having a disintegratable ball or plug check.In addition, the subassembly may be used, without any specialty parts,as a flow back plug. Thus, a variety of down hole tools or plugs may beassembled from a common subassembly and a few specialty parts thatprovide the special functions of different plugs. In one aspect, asupplier does not have to keep so much inventory because one alwaysseems to receive orders for what is in short supply. Another majoradvantage of the disclosed device is that a subassembly and a packagecontaining the specialty parts may be shipped to a supply store customeror to an operator customer. In some embodiments, the customer may usethe shipped subassembly as a ball drop tool or may remove one end fromthe tool and insert one of the specialty parts in a recess at the end ofthe tool and thereby convert the subassembly to a bridge plug or a flowback plug.

An important advantage of the combination well tool disclosed herein isthat the specialty parts may be incorporated into the subassemblywithout having to take the subassembly apart and then reassemble it.This is accomplished by adding the specialty parts through one end andleaving the opposite end of the subassembly intact.

The subassembly parts that are common to the down hole plugs disclosedherein are, in some embodiments, a mandrel, the elements of a slips/sealsection, a mule shoe and a setting assembly that, when the plug ismanipulated by a conventional setting tool, expands the slips/sealsection into sealing engagement with the inside of a production or pipestring. An important advantage of this subassembly is that manipulatingthe tool to set the slips creates a passageway through the settingassembly and, in some embodiments, through the plug. This allows theassembly of a bridge plug, a flow back plug, a ball drop plug or a plughaving a disintegratable valve simply by the addition of specializedparts.

In some embodiments, the common subassembly is a mandrel, the elementsof a slips/seal section and a mule shoe. In these embodiments, the plugis expanded by pulling on the mandrel and/or pushing on the slips/sealsection to expand the slips/seal section in a conventional manner. Inapplication Ser. No. 12/317,497, the common assembly includes a separatesetting device attached to the mandrel and a setting rod threaded intothe setting device. Pulling sufficiently on the setting rod strips thethreads and releases the setting rod thereby opening a passage throughthe mandrel thereby allowing separate components to be inserted into thepassage to provide a bridge plug, a flow back plug, a ball drop plug andthe like.

In some embodiments of this invention, the setting device comprises athreaded upper end of the mandrel and the setting rod comprises athreaded member received in the threaded upper end of the mandrel. Inthese embodiments, a portion of the mandrel spaced below the threads,i.e. distanced further from the surface of the earth, is of reducedthickness so pulling on the setting rod first causes the slips/sealsection to expand into engagement with the inside of a production stringand then causes the mandrel to fail thereby opening a passage, orincreasing the internal passage, through the mandrel. This commonsubassembly allows additional elements to be added to create a bridgeplug, a flow back plug, a ball drop plug and the like.

An important advantage of this invention is the specialty parts added tothe common subassembly are conveniently added to one end of the commonsubassembly without having to take the subassembly apart. In someembodiments, the specialty parts may be added to a top of thesubassembly and, in other embodiments, may be added to a bottom of thesubassembly.

It is an object of this invention to provide an improved down hole wellsubassembly that is easily adapted to provide different functions.

Another object of this invention is to provide an improved down holesubassembly where specialty parts may be added to one end of thesubassembly without having to take the subassembly apart.

A more specific object of this invention is to provide an improved downhole plug in which a setting rod is tensioned to set the plug on theinside of a production or pipe string and then pulled out of the plug.

Another object of this invention is to provide an improved method ofdistributing down hole well tools.

These and other objects and advantages of this invention will becomemore apparent as this description proceeds, reference being made to theaccompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a subassembly which is readilymodified to act as a variety of tools and which also comprises a balldrop plug, illustrated in a running in or extended position;

FIG. 2 is a cross-sectional view of the ball drop plug of FIG. 1,illustrated in a set or collapsed position;

FIG. 3 is a cross-sectional view of a flow back plug illustrated in arunning in or extended position;

FIG. 4 is an enlarged cross-sectional view of a bridge plug, illustratedin a running in or extended position;

FIG. 5 is a schematic view of a subassembly and a container havingtherein specialty parts for converting the subassembly to one of avariety of down hole tools; and

FIG. 6 is a cross-sectional view of another common subassembly or flowback plug.

DETAILED DESCRIPTION

The present invention relates to devices for use in hydrocarbon wellsdrilled into the earth and completed using a variety of techniques. Thematerials from which the tools are made are subject to considerablevariation. Some of the components are made of metals and some are madeof composite plastics. Any components left in the well are usually madeof drillable materials. Various changes and adaptations may be made inthe tools without departing from the spirit and scope of the invention,which is to be measured solely by the claims themselves.

Referring to FIGS. 1-2, there is illustrated a subassembly 10 which isusable, without modification, as a ball drop plug and which may have afew components added to it to provide a flow back plug 12 shown in FIG.3 or a bridge plug 14 as shown in FIG. 4. The subassembly 10, the flowback plug 12 and the bridge plug 14 may comprise, as major components insome embodiments, mandrels 20, slips/seal sections or assemblies 22,setting assemblies 24 and mule shoes 26. Because it is often desired todrill out the plugs 10, 12, 14 the components left in the well aretypically made of drillable materials, such as composite plastics,aluminum, bronze, cast iron or other drillable materials. Compositeplastics are well known in the art and are of a variety of types, suchas a fabric impregnated with a suitable resin and allowed to cure, awound fiberglass filament resin impregnated material, a fiber moldedinjection impregnated material or the like.

The mandrel 20 may provide a central axial passage 28, a threadedsection 30 intermediate the ends of the mandrel 20, a tapered or valveseat section 32 above the threads 30 and an upper threaded section 34. Aretaining sleeve 37 may be attached to the upper end of the mandrel 20in any suitable manner, as by threads, set screws, pins or the like. Thewords upper and lower are somewhat inaccurate because they refer to theposition of the well tools as if they were in a vertical position whilemany, if not most, of the plugs disclosed herein will be used primarilyin horizontal wells. The words upper and lower are used for purposes ofconvenience rather than the more accurate proximal and distal. The lowerend 38 of the mandrel 20 is threaded for connection to the mule shoe 26as will be more fully apparent hereinafter.

The slips/seal section 22 may be more-or-less conventional and providesone or more resilient seals 40 and one or more wedge shaped elements 42which abut wedge shaped slips 44, 46 having wickers or teeth. Theelements 42 are conveniently pinned to the mandrel 20 by set screws,plastic bolts or pins (not shown) so the seals 40 and elements 42 stayin place during handling. The set screws, plastic bolts or pins (notshown) are easily sheared during setting of the plugs 10, 12, 14. Theupper slips 44 abut a ring 48 while the lower slips 46 abut a squareshoulder provided by the mule shoe 26.

The setting assembly 24 includes a setting rod 50 connected to themandrel 20 and may have a lower threaded end 52 received in the threads34. The setting assembly 24 includes some mechanism to separate thesetting rod 50 from the mandrel 20 and unblock or open the mandrelpassage 28. This mechanism may be of any suitable type such as such asshear pins or shear screws extending through the mandrel 20 into thesetting rod 50 or may comprise a reduced diameter, partible or neckeddown section 36 of the mandrel 20. Thus, in the vocabulary of Ser. No.12/317,497, the threads 34 and partible neck 36 or the shear pins/screwscomprise a setting device. Because the setting rod 50 is removed fromthe well, in most embodiments it is normally not made of a drillablematerial and is typically of steel. As is apparent, the setting deviceor threads 34 and/or necked down section 36 may provide a passagetherethrough. The setting rod 50 may be solid, i.e. have no passagetherethrough, or may be tubular having a passage therethrough. It willbe seen that part of the necked down or partible section 36 may providethe tapered valve seat 32.

When setting the plugs 10, 12, 14 the setting tool (not shown) pulls onthe setting rod 50 and/or pushes on the load ring 48, the slips/sealsection 22 expands to set the seals 40 and the slips 44, 46 against aproduction or pipe string in the well. The rod 50 may be pulledcompletely out of the mandrel passage 28 and it is desirable that therod 50 pull out of the mandrel 20 in response to a predictable force. Tothis end, the material of the mandrel 28 and the thickness of the neckeddown section 36 are selected to fail at a predictable tensile force.

The mule shoe 26 comprises the lower end of the subassembly 10 anddiffers from the device shown in application Ser. No. 12/317,497 becausethe function altering components are at the top or proximal end of theplugs 10, 12, 14 rather than at the bottom or distal end. The mule shoeincludes a body 54 having a tapered lower end 56 and a passage 58opening through the lower end 56. The mule shoe 26 includes an upper end60 abutting the bottom of the lower slip 46 and a series of grooves 62which allow completion fluids to pass more readily around the mule shoe26 at appropriate times, for example when the plug is being pulled by awireline upwardly in a liquid filled well. A pump down collar 64 slipsover the lower end of the mule shoe 26 so the plug may be pumped into ahorizontal leg of a well. In some embodiments, the mule shoe 26 may bepinned to the mandrel 20 so it won't become unthreaded.

No special components need to be added to the subassembly 10 to providethe ball drop plug. In other words, the ball drop plug and thesubassembly 10 are identical. Thus, in one mode of operation, a ballcheck 66 is dropped into a production or pipe string (not shown) afterthe subassembly 10 is expanded against the production string to seatagainst the tapered inlet 32. Those skilled in the art will recognizethat the ball drop plug 10 can be used in a situation where a series ofzones are to be fraced. There are a number of ways that ball drop plugsare conventionally used, one of which is to frac a zone, run a ball dropplug 10 into the well above the fraced zone, drop a ball 66 into theproduction string and thereby isolate the lower zone so a higher zonemay be fraced. In another mode of operation, the mandrel 20 may belengthened above the necked down section 36 as suggested by the breaklines in FIG. 1 to provide a recess to receive the ball check 66 whichmay be incorporated into the subassembly 10 before it is run into awell, as suggested by the break lines in FIG. 1. In the alternative, thesetting rod 50 may provide a cavity 67 to receive a ball check 66incorporated into the subassembly 10 before it is run into a well, asshown in dotted lines in FIG. 1.

In order to assemble the flow back plug 12 from the subassembly 10, itis necessary only to insert a ball check assembly 68 on the threads 30.This may be accomplished by removing the setting rod 50, if necessary,and inserting the ball check assembly 68 into the upper end of themandrel 20. It will be apparent to those skilled in the art that theflow back plug 12 is often used in situations where a series of zonesare to be fraced in a well. After a zone is fraced, the flow back plug12 is run into the well and expanded against a production string. Theball check assembly 68 prevents flow through the plug 12 is a downwarddirection in a vertical well but allows the fraced zone to produce upthe production string. The ball check assembly 68 comprises a housing 70which may include threads 72 meshing with the threads 30 on the insideof the mandrel 20 or the housing 70 may be captivated in the mandrel 20in any suitable manner. The housing 70 provides O-rings 74 sealingbetween the housing 70 and the mandrel 20 and a pin 76 or otherrestraint preventing a ball 78 from flowing upwardly out of the plug 12.

In order to assemble the bridge plug 14, it is necessary only to insertan obstruction 80 onto the threads 30. In some embodiments, theobstruction 80 includes an imperforate housing 82 having one or moreO-rings or other seals 84 engaging the inside of the mandrel 20. Threads86 may be provided for coupling with the threads 30 of the mandrel 20 orthe housing 82 may be captivated inside the mandrel 20 in any suitablemanner. It will be seen to those skilled in the art that the bridge plug14 prevents flow, in either direction, through the plug 14 so the plug14 is used in any situation where bridge plugs are commonly used.

It will be apparent that the ball check 66 or the ball check 78 may bemade of a disintegratable material so the check valve action of theseplugs is eliminated over time.

In use, the subassembly 10 and a package containing the ball check 66,the valve assembly 68 and the obstruction 80, and the setting rod 50 areshipped to a supply store or customer. The subassembly 10 may be shippedwith the setting rod 50 assembled or in the package 88. Customizing thesubassembly 10 may be done at any time simply by opening the package,retrieving the desired specialty component and/or the setting rod 50,inserting the desired specialty component in the mandrel passage 28 andinstalling setting rod 50. Thus, customizing the subassembly 10 may bedone at a supply store, at a shop of the operator or service company, atthe well location or at any other suitable time after receipt by thecustomer or its representative.

The plugs 10, 12, 14 are set in a conventional manner using aconventional setting tool (not shown) such as a Model 10, 20, E-4, orE-5 Setting Tool available from Baker Oil Tools, Inc., Houston, Tex.,and appropriate connector subs are attached to the setting rod 50 of theplug being set and an annular member rides over the upper section end ofthe mandrel 20 to abut the load ring 48, which is the uppermostcomponent of the slips/seat section 22. When this assembly has beenlowered to the desired location in a vertical well or pumped to thedesired location in a horizontal well, the setting tool is actuated totension the rod 50 and/or compress the load ring 48. This shears off theplastic screws 86 so the slips 44, 46 slide toward each other on theexterior of the mandrel 20. This forces the resilient seals 40 outwardlyto seal against the inside of the production string and expands theslips 44, 46 so the withers grip the inside of the production string andset the plug in place. Continued pulling on the rod 50 pulls the neck 32of the mandrel 20 in two thereby releasing the rod 50 which is withdrawnfrom the mandrel 20. This may leave the passage 28 open through itsmaximum internal diameter through the mandrel 20. This allows thesubassembly 10 to be used without modification as a ball drop plug, tobe configured as the flow back plug 12 of FIG. 3 or the bridge plug 14of FIG. 4. It will be evident that FIG. 2 is misleading in the sensethat the setting assembly 50 has sheared off from the mandrel 20 but theslips/seal section 22 is not illustrated as being expanded. In fact, theslips/seal section 22 expands first and the setting rod 50 then shearsoff.

Although the function of the subassembly 10 is modified by inserting thespecialty parts into the top of the tool, the same function can beaccomplished by providing a cavity or recess between the bottom of themandrel 20 and the mule shoe 26 for receiving a check valve assemblyanalogous to the assembly 68 and/or an obstruction analogous to theobstruction 80. In the embodiments previously described, the mule shoe26 may be pinned or otherwise secured to prevent unthreading of the muleshoe 26 from the mandrel 20. In embodiments where the specialty partsare to be installed at the bottom of the subassembly 10, the mule shoe26 is simply threaded onto the mandrel 20 and any pinning of the muleshoe 26, if desired, is accomplished after the specialty parts areinstalled.

As shown in FIG. 5, it will be apparent that the subassembly 10 may beshipped to a customer along with a container 88 having therein the ballcheck 66, the ball check assembly 68 and the obstruction 80 so the plugneeded may be assembled in the field by a wire line operator. It will beapparent that the subassembly 10 and container 88 may be packagedtogether or shipped separately to a customer.

Referring to FIG. 6, there is illustrated another embodiment 90 whichserves as a ball drop plug or subassembly for another family of bottomhole tools analogous to FIGS. 1-4. As illustrated, the subassembly 90 isa combination of some components from FIGS. 1-4 and some components fromapplication Ser. No. 12/317,497. The subassembly 90 comprises, as majorcomponents, a mandrel 92, a slips/seal section 94, a setting assembly 96and a mule shoe 98. The mandrel 92 includes an interior passage 100having threads 102 at a suitable location to receive a ball checkassembly analogous to the ball check assembly 68 or an obstructionanalogous to the obstruction 80. The mandrel 92 includes an uppertapered ball seat surface 104 for sealably receiving a ball checkanalogous to the ball check 66. The mandrel 92 may also comprise aretaining sleeve 106 to keep the components of the slips/seal section 94in assembled condition.

A substantial difference between the subassemblies 10 and 90 lies in adifferent technique for expanding the plug. More specifically, thesetting assembly 96 comprises an elongate rod 108 which is pinned to themandrel 92 or the mule shoe 98 by one or more shear pins 110 extendingthrough openings 112 into a recess 114 in the rod 108. The shear pins110 are selected to shear or fail at a predetermined load appliedbetween the mandrel 92 and the rod 108 thereby expanding the slips/sealsection 94.

It will be seen that the subassembly 90 includes a setting devicecomprising the connection between the mandrel 92 or mule shoe 98 and thesetting rod 108.

The subassembly 90 is set in a conventional manner, i.e. a setting toolconnects to the setting rod 96 and pushes on the upper load ring 116and/or pulls on the mandrel 92 thereby expanding the slips/seal section94 and ultimately shearing the pins 110. This releases the rod 108 whichis pulled from the mandrel 92 thereby operating in much the same manneras the device of Ser. No. 12/317,497.

Although this down hole tool has been disclosed and described in itspreferred forms with a certain degree of particularity, it is understoodthat the present disclosure of the preferred forms is only by way ofexample and that numerous changes in the details of operation and in thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and scope of the invention as hereinafterclaimed.

1. A down hole well tool comprising a mandrel having an upper end, alower end and a passage between the ends; a slips/seal section movableon an exterior of the mandrel from a running in position to an expandedposition for sealing against a production string; a setting assemblyassisting in moving the slips/seal section from the running in positionto the expanded position, the setting assembly including a settingdevice rigid with the mandrel having a partible section adjacent anupper end of the mandrel and distant from the lower end of the mandrelfor failing at a predetermined load to separate the setting device fromthe mandrel, and a setting rod connected to the setting device so thattensioning on the setting rod parts the setting device, expands theslips/seal section into sealing engagement with the production stringand removes the setting rod from the mandrel, the arrangement of thesetting device and setting rod being that removal of the setting rodfrom the tool unblocks the mandrel passage.
 2. The down hole tool ofclaim 1 wherein the partible section includes a reduced thicknesssection of the mandrel.
 3. The down hole tool of claim 2 wherein thereduced thickness section includes a tapered section on the mandrelacting as a seat for a ball check.
 4. The down hole tool of claim 1wherein the mandrel passage includes a cavity below the partible sectionand further comprising a ball check assembly captivated in the cavityallowing upward flow through the mandrel passageway and preventingdownward flow therethrough.
 5. The down hole tool of claim 1 wherein themandrel passage provides a tapered section below the partible sectionacting as a seat for a ball check.
 6. The down hole tool of claim 5further comprising a ball check seated against the tapered sectionpreventing downward flow into the production string.
 7. The down holetool of claim 1 wherein the mandrel passageway provides a cavity andfurther comprising an obstruction in the cavity below the partiblesection preventing upward flow through mandrel passage and preventingdownward flow therethrough.
 8. The down hole tool of claim 1 wherein thesetting rod is a solid member having no passage therethrough.
 9. Thedown hole tool of claim 1 wherein the mandrel passageway provides acavity having threads and a threaded obstruction connected to the cavitythreads converting the down hole tool to a bridge plug.
 10. The downhole tool of claim 1 wherein the setting rod is removably attached tothe mandrel and, upon removal from the mandrel, exposes a cavity havinga check valve assembly therein.
 11. The down hole tool of claim 1wherein the setting rod is removably attached to the mandrel and, uponremoval from the mandrel, exposes a cavity having an obstruction thereinblocking the mandrel passage and converting the down hole tool into abridge plug.
 12. The down hole tool of claim 1 wherein the setting rodis removably attached to the mandrel and, upon removal from the mandrel,exposes a cavity having a ball check converting the down hole tool intoa ball drop plug.
 13. A method of distributing a combination down holewell tool having a plurality of functions, comprising shipping to acustomer a subassembly including a mandrel having an upper end, a lowerend and a passage between the ends, a slips/seal section movable on anexterior of the mandrel from a running in position to an expandedposition for sealing against a production string and a setting assemblyassisting in moving the slips/seal section from the running in positionto the expanded position; shipping to the customer a container havingtherein specialty parts comprising a check valve assembly for convertingthe subassembly into a flow back plug and an obstruction for convertingthe subassembly into a bridge plug; and after the subassembly and thecontainer are shipped to the customer, customizing the subassembly byopening the container and retrieving one of the specialty parts andinstalling the specialty part in the subassembly.
 14. The method ofclaim 13 wherein the subassembly and the container are shipped to thecustomer in a single package.
 15. The method of claim 13 wherein thesubassembly includes a setting rod for actuating the setting assembly,the setting rod being assembled on the subassembly when it is shipped tothe customer.
 16. The method of claim 13 wherein the container includestherein a setting rod for actuating the setting assembly, the settingrod being assembled on the subassembly after the container is opened.17. The method of claim 13 wherein the container further comprises aball check separate from the check valve assembly.
 18. The method ofclaim 13 wherein the container further comprises a disintegratablecheck.